Turbulent Combustion of Polydisperse Evaporating Sprays with Droplet Crossing: Eulerian Modeling and Validation in the Infinite Knudsen Limit

The accurate simulation of the dynamics of polydisperse evaporating sprays in unsteady gaseous flows with large-scale vortical structures is both a crucial issue for industrial applications and a challenge for modeling and scientific computing. The difficulties encountered by the usual Lagrangian approaches make the use of Eulerian models attractive, aiming at a lower cost and an easier coupling with the carrier gaseous phase. Among these models, the multi-fluid model allows for a detailed description of the polydispersity and size-velocity correlations for droplets of various sizes. The purpose of the present study is twofold. First, we extend the multi-fluid model in order to cope with crossing droplet trajectories by using the quadrature method of moments in velocity phase space conditioned by size. We identify the numerical difficulties and provide dedicated numerical schemes in order to preserve the velocity moment space. Second, we conduct a comparison study and demonstrate the capability of such an approach to capture the dynamics of an evaporating polydisperse spray in a 2-D free jet configuration. We evaluate the accuracy and computational cost of Eulerian models and related discretization schemes vs. Lagrangian solvers and show that, even for finite Stokes number, the standard Eulerian multi-fluid model can be accurate at reasonable cost

Potential health impacts of heavy metals on HIV-infected population in USA.

Noninfectious comorbidities such as cardiovascular diseases have become increasingly prevalent and occur earlier in life in persons with HIV infection. Despite the emerging body of literature linking environmental exposures to chronic disease outcomes in the general population, the impacts of environmental exposures have received little attention in HIV-infected population. The aim of this study is to investigate whether individuals living with HIV have elevated prevalence of heavy metals compared to non-HIV infected individuals in United States. We used the National Health and Nutrition Examination Survey (NHANES) 2003-2010 to compare exposures to heavy metals including cadmium, lead, and total mercury in HIV infected and non-HIV infected subjects. In this cross-sectional study, we found that HIV-infected individuals had higher concentrations of all heavy metals than the non-HIV infected group. In a multivariate linear regression model, HIV status was significantly associated with increased blood cadmium (p=0.03) after adjusting for age, sex, race, education, poverty income ratio, and smoking. However, HIV status was not statistically associated with lead or mercury levels after adjusting for the same covariates. Our findings suggest that HIV-infected patients might be significantly more exposed to cadmium compared to non-HIV infected individuals which could contribute to higher prevalence of chronic diseases among HIV-infected subjects. Further research is warranted to identify sources of exposure and to understand more about specific health outcomes

Depletion of B2 but Not B1a B Cells in BAFF Receptor-Deficient ApoE−/− Mice Attenuates Atherosclerosis by Potently Ameliorating Arterial Inflammation

We have recently identified conventional B2 cells as atherogenic and B1a cells as atheroprotective in hypercholesterolemic ApoE−/− mice. Here, we examined the development of atherosclerosis in BAFF-R deficient ApoE−/− mice because B2 cells but not B1a cells are selectively depleted in BAFF-R deficient mice. We fed BAFF-R−/− ApoE−/− (BaffR.ApoE DKO) and BAFF-R+/+ApoE−/− (ApoE KO) mice a high fat diet (HFD) for 8-weeks. B2 cells were significantly reduced by 82%, 81%, 94%, 72% in blood, peritoneal fluid, spleen and peripheral lymph nodes respectively; while B1a cells and non-B lymphocytes were unaffected. Aortic atherosclerotic lesions assessed by oil red-O stained-lipid accumulation and CD68+ macrophage accumulation were decreased by 44% and 50% respectively. B cells were absent in atherosclerotic lesions of BaffR.ApoE DKO mice as were IgG1 and IgG2a immunoglobulins produced by B2 cells, despite low but measurable numbers of B2 cells and IgG1 and IgG2a immunoglobulin concentrations in plasma. Plasma IgM and IgM deposits in atherosclerotic lesions were also reduced. BAFF-R deficiency in ApoE−/− mice was also associated with a reduced expression of VCAM-1 and fewer macrophages, dendritic cells, CD4+ and CD8+ T cell infiltrates and PCNA+ cells in lesions. The expression of proinflammatory cytokines, TNF-α, IL1-β and proinflammatory chemokine MCP-1 was also reduced. Body weight and plasma cholesterols were unaffected in BaffR.ApoE DKO mice. Our data indicate that B2 cells are important contributors to the development of atherosclerosis and that targeting the BAFF-R to specifically reduce atherogenic B2 cell numbers while preserving atheroprotective B1a cell numbers may be a potential therapeutic strategy to reduce atherosclerosis by potently reducing arterial inflammation

Turbulent Combustion of Polydisperse Evaporating Sprays with Droplet Crossing: Eulerian Modeling and Validation in the Infinite Knudsen Limit

The accurate simulation of the dynamics of polydisperse evaporating sprays in unsteady gaseous flows with large-scale vortical structures is both a crucial issue for industrial applications and a challenge for modeling and scientific computing. The difficulties encountered by the usual Lagrangian approaches make the use of Eulerian models attractive, aiming at a lower cost and an easier coupling with the carrier gaseous phase. Among these models, the multi-fluid model allows for a detailed description of the polydispersity and size-velocity correlations for droplets of various sizes. The purpose of the present study is twofold. First, we extend the multi-fluid model in order to cope with crossing droplet trajectories by using the quadrature method of moments in velocity phase space conditioned by size. We identify the numerical difficulties and provide dedicated numerical schemes in order to preserve the velocity moment space. Second, we conduct a comparison study and demonstrate the capability of such an approach to capture the dynamics of an evaporating polydisperse spray in a 2-D free jet configuration. We evaluate the accuracy and computational cost of Eulerian models and related discretization schemes vs. Lagrangian solvers and show that, even for finite Stokes number, the standard Eulerian multi-fluid model can be accurate at reasonable cost.This article is from Proceedings of the 2008 Summer Program, Center for Turbulence Research, Stanford, CA, pp.265-276.</p

Turbulent combustion of polydisperse evaporating sprays with droplet crossing: Eulerian modeling of collisions at finite Knudsen and validation

International audienceThe accurate simulation of the dynamics of polydisperse sprays in unsteady gaseous flows with large-scale vortical structures is both a crucial issue for industrial applications and a challenge for modeling and scientific computing. In a companion paper, we have shown the capability of the Eulerian multi-fluid model to capture the dynamics and evaporation of such sprays and extended it in order to handle finite Stokes number crossing droplet trajectories, by using quadrature method of moments in velocity phase space conditioned on droplet size. Such a study was conducted in the limit of infinite Knudsen numbers. In this paper, we investigate a potential extension of such an approach in order to capture the dynamics of polydisperse spray collisions modeled by a Boltzmann operator at the mesoscopic level of description for finite Knudsen numbers. After deriving the model and presenting the dedicated numerical methods needed to preserve the moment space, we validate this approach and its capability of describing collisional crossing jets by comparing the results for both monodisperse and polydisperse clouds of particles with Lagrangian discrete particle simulations

Identification of T‐cell epitopes from benzylpenicillin conjugated to human serum albumin and implication in penicillin allergy

International audienceAbstract Background There is in vitro evidence that T cells from allergic patients react to benzylpenicillin‐human serum albumin ( BP ‐ HSA ) bioconjugates. Our group has recently shown the existence of naïve CD 4 + T cells recognizing BP ‐ HSA in healthy donors. However, BP ‐haptenated peptides from HSA participating in the immunization of allergic patients have never been identified. The purpose of the present study is to identify immunodominant BP ‐haptenated peptides from HSA involved in immunization of patients to BP and to refine the frequency calculation of naïve CD 4 + T cells recognizing BP . Methods Co‐cultures were established with CD 4 + T cells from non‐allergic donors and mature autologous dendritic cells ( DC s) loaded with BP ‐ HSA or BP ‐haptenated peptides from HSA . The CD 4 + T‐cell response specific for BP ‐ HSA or for individual BP ‐haptenated peptides was measured using an interferon‐γ ( IFN ‐γ) ELIS pot assay. The frequency of BP ‐specific CD 4 + T cells was then calculated using the Poisson distribution. BP ‐ HSA and BP ‐haptenated peptides recognition by allergic patients was evaluated on peripheral blood mononuclear cells ( PBMC s) using a lymphocyte transformation test ( LTT ). Results Results showed that BP ‐ HSA and BP ‐haptenated peptides were recognized by naïve T cells from 15/16 and 13/14 tested healthy donors, respectively. Most donors responded to 3 peptides with BP covalently bound on lysines 159, 212, and 525. Two of these benzylpenicilloylated peptides (lysines 159 and 525) were also found to induce PBMC s proliferation in patients with allergic reaction to penicillins. Conclusion This study identifies and characterizes for the first time the BP ‐haptenated peptides from HSA involved in the immunization of patients to penicillins